An HDMI has become popular as a digital interface for the transmission of video and audio. In this HDMI, an audio transmission function or a copyright protection function is added to a DVI (Digital Visual Interface) which is a connection standard between a PC (Personal Computer) and a display and the resultant configuration is arranged for an AV (Audio Visual) device.
In the HDMI standard, inter-device control using a CEC is defined. According to this CEC, a variety of functions can be controlled on the basis of unique physical addresses and logical addresses which can be allocated to devices existing in an HDMI network.
For example, when a DVD player HDMI-connected to a television receiver starts its reproduction while a user is viewing digital broadcasting with the television receiver, the television receiver is automatically switched to an input state where the DVD player is connected to the television receiver so as to perform a CEC combination operation (For example, JP-A-2010-130068).
Accordingly, as a basic function of the CEC, there is an advantage that the user can switch the operating mode to a state where the user can view a video and an audio reproduced by the DVD player by only pressing a playback button of the DVD player without performing an input switching operation on the television receiver. In addition, the user can also operate the menu displayed by the DVD player or ON and OFF states of a power supply by the use of a remote controller of the television receiver.
In the HDMI standard, a CEC message (<Active Source>) indicating an output device which displays a video on the television receiver is defined. Actually, when the user operates a playback button of the DVD player coping with the HDMI standard and the DVD player is in a state where it can output a video signal (that is, in an active state), the DVD player outputs an AV stream and broadcasts the CEC message (<Active Source>) indicating that it is an active device.
Here, the broadcasting means simultaneous transmission of signals to all devices, not to a specific device, as a destination. The television receiver and the other external devices to which the CEC message (<Active Source>) is broadcast from the DVD player switch a path for reproducing the AV stream output from the DVD player.
In this way, the HDMI standard defines that a device (the DVD player in this case) displaying a video on the television receiver broadcasts the CEC message (<Active Source>) to the other devices in the network. In addition, the CEC message (<Active Source>) is one of the CEC messages defined in the HDMI standard.